Topic Contents

Stool Analysis

Test Overview

A stool analysis
is a series of tests done on a stool (feces) sample to help diagnose certain
conditions affecting the
digestive tract. These conditions can include
infection (such as from
parasites,
viruses, or
bacteria), poor nutrient absorption, or cancer.

For a stool analysis, a stool sample is collected in a clean
container and then sent to the laboratory. Laboratory analysis includes
microscopic examination, chemical tests, and microbiologic tests. The stool
will be checked for color, consistency, amount, shape, odor, and the
presence of mucus. The stool may be examined for hidden (occult) blood, fat,
meat fibers,
bile,
white blood cells, and sugars called reducing
substances. The
pH of the stool also may be measured. A stool
culture is done to find out if bacteria may be causing
an infection.

Why It Is Done

Stool analysis is done to:

Help identify diseases of the digestive tract,
liver, and
pancreas. Certain
enzymes (such as trypsin or elastase) may be evaluated
in the stool to help determine how well the pancreas is functioning.

Help find the cause of symptoms affecting the digestive tract,
including prolonged diarrhea, bloody diarrhea, an increased amount of gas,
nausea, vomiting, loss of appetite, bloating, abdominal pain and cramping, and
fever.

Look for the cause of an infection, such as
bacteria, a
fungus, or a virus.

Check for poor
absorption of nutrients by the digestive tract (malabsorption syndrome). For
this test, all stool is collected over a 72-hour period and then checked for
fat (and sometimes for meat fibers). This test is called a 72-hour stool collection or
quantitative fecal fat test.

Talk to your doctor about any concerns you have regarding
the need for the test, its risks, how it will be done, or what the results will
mean. To help you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).

How To Prepare

Many medicines can change the results
of this test. You will need to avoid certain medicines depending on which
kind of stool analysis you have. You may need to stop taking medicines such as
antacids, antidiarrheal medicines, antiparasite medicines, antibiotics,
laxatives, or
nonsteroidal anti-inflammatory drugs (NSAIDs) for 1 to
2 weeks before you have the test. Be sure to tell your doctor about all the
nonprescription and prescription medicines you take.

Traveled in recent weeks or
months, especially if you have traveled outside the country. This helps your doctor look for the parasites, fungi,
viruses, or bacteria that may be causing a problem.

If your stool is being tested for blood, you may need to avoid certain foods for 2 to 3 days before the test. This depends on what kind of stool test you use. And do not do the test during your menstrual period or if you have active bleeding from hemorrhoids. If you aren't sure about how to prepare, ask your doctor.

Do not use a stool sample for testing that has been in contact with toilet bowl cleaning products that turn the water blue.

How It Is Done

Stool samples can be collected at home,
in your doctor's office, at a medical clinic, or at the hospital. If you
collect the samples at home, you will be given stool collection kits to use
each day. Each kit contains applicator sticks and two sterile
containers.

You may need to collect more than one sample over 1 to
3 days. Follow the same procedure for each day.

Collect the
samples as follows:

Urinate before collecting the stool so that you
do not get any urine in the stool sample.

Pass stool (but no
urine) into a dry container. You may be given a plastic basin that can be
placed under the toilet seat to catch the stool.

Either solid or liquid stool can be
collected.

If you have diarrhea, a large plastic bag taped to the
toilet seat may make the collection process easier; the bag is then placed in a
plastic container.

If you are constipated, you may be given a small
enema.

Do not collect the sample from the toilet
bowl.

Do not mix toilet paper, water, or soap with the sample.

Place the lid on the container and label it with your name, your
doctor's name, and the date the stool was collected. Use one container for each
day's collection, and collect a sample only once a day unless your doctor gives
you other directions.

Take the sealed container to your doctor's office or the
laboratory as soon as possible. You may need to deliver your sample to the lab
within a certain time. Tell your doctor if you think you may have trouble
getting the sample to the lab on time.

If the stool is collected
in your doctor's office or the hospital, you will pass the stool in a plastic
container that is inserted under the toilet seat or in a bedpan. A health
professional will package the sample for laboratory analysis.

You
will need to collect stool for 3 days in a row if the sample is being tested
for quantitative fats. You will begin collecting stool on the morning of the
first day. The samples are placed in a large container and then
refrigerated.

You may need to collect several stool samples over 7
to 10 days if you have digestive symptoms after traveling outside the
country.

Samples from babies and young children may be collected
from diapers (if the stool is not contaminated with urine) or from a
small-diameter glass tube inserted into the baby's rectum while the baby is
held on an adult's lap.

Sometimes a stool sample is collected
using a rectal swab that contains a preservative. The swab is inserted into the
rectum, rotated gently, and then withdrawn. It is placed in a clean, dry
container and sent to the lab right away.

How It Feels

There is no pain while collecting a stool
sample. If you are constipated, straining to pass stool may be painful.

If your health professional uses a rectal swab to collect the sample, you
may feel some pressure or discomfort as the swab is inserted into your
rectum.

Risks

Any stool sample may contain germs that can
spread disease. It is important to carefully
wash your hands and use careful handling techniques to avoid spreading
infection.

Results

A stool analysis is a series of tests
done on a stool (feces) sample to help diagnose certain conditions affecting
the digestive tract.

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

What To Think About

A stool
culture is done to find the cause of an infection, such as bacteria, a virus, a
fungus, or a parasite. To learn more, see the topic
Stool Culture.

A bowel transit time test
is done to help find the cause of abnormal movement of food through the
digestive tract. To learn more, see the topic
Bowel Transit Time.

The D-xylose
absorption test is done to help diagnose problems that prevent the small
intestine from absorbing nutrients in food. This test may be done when symptoms
of malabsorption syndrome (such as chronic diarrhea, weight loss, and weakness)
are present. To learn more, see the topic
D-Xylose Absorption Test.

A stool analysis
to measure trypsin or elastase is not as reliable as the sweat test to detect
cystic fibrosis. To learn more, see the topic
Sweat Test.

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